For example, a heat engine is described in Patent Document 1 (JP 2004-84523A corresponding to US 2004/0060294A1) and Patent Document 2 (JP 10-252556A). In the heat engine of Patent Document 1, the liquid piston made of a liquid fluid is sealed in a tube container, and a part of the liquid piston is heated by a heating portion provided at one end side of the container so as to generate vapor. The vapor is cooled and condensed in a cooling portion formed at a middle portion of the container, thereby causing a volume change of the vapor. By the volume change of the vapor in the container, the liquid piston is displaced in the container so that the displacement of the liquid piston is converted to a mechanical energy in the heat engine.
In the heat engine described in Patent Document 2, a liquid piston made of a liquid fluid is sealed in a main container, and a liquid is sealed in a separation container separated from the main container. Vapor is generated by heating the liquid sealed in the separation container, and is supplied to one end portion of the main container at a predetermined timing. Then, the vapor is cooled and condensed in a cooling portion provided at a middle portion of the main container, so that the liquid piston is displaced to be reciprocated in the main container.
In the heat engine of Patent Document 1, a part of the liquid fluid as the liquid piston is evaporated by the heating portion. When the liquid piston is moved to a cooling portion without being evaporated in the heating portion, the liquid piston is adapted to only transfer the heat quantity from the heating portion to the cooling portion, and thereby the heat quantity from the heating portion becomes heat loss and cannot be output as the mechanical energy. Because heat loss (heat transferring loss) is generated, an energy conversion efficiency from the heat energy to the mechanical energy is decreased.
In the heat engine of Patent Document 2, because the liquid in the separation container separated from the main container is heated to generate the vapor, the above problem of the Patent Document 1 is not caused.
However, in the heat engine of the Patent Document 2, it is difficult to avoid that a non-condensable gas (e.g., air) mixes in the vapor supplied to the main container and the non-condensable gas is accumulated into the main container. Thus, not only a compression loss for compressing the non-condensable gas occurs, but also the cooling of the vapor in the cooling portion is restricted by the non-condensable gas, and thereby a loss for compressing the vapor, which is not condensed by the cooling portion, is caused.
As a result, the heat energy conversion efficiency is decreased.
The present invention is made in view of the above matters, and it is an object of the present invention to provide a heat engine, which can effectively improve heat energy conversion efficiency.